I’ve created an Arduino shield to control Lego Motors:
It will be sold as a kit with all of teh required components included.
An Android app to control the shield is under development, and will go on the Google Play store if the project is funded.
It is powered from a Power Functions plug, and has 3 channels that can be controlled via bluetooth with the Android app, or programmed with the Arduino or the in-app programming interface in the Android app.
See the kickstarter for more info, plus demo videos and information and demos of the android app: http://kck.st/1KqXFFV, and if you want one, please consider backing it.
What are your opinions on it, or do you have any improvements to suggest?